Cloud Radius Server

[Phil Mayers]

On 09/26/2012 11:42 PM, Michael Geary wrote:
> Good Evening,
>
> We have several separate networks. Our main network runs PPPoE while all
> of the others run over DHCP. I would like to migrate the DHCP networks
> to use PPPoE.

I assume these are Ethernet-over-ADSL lines and you want to move away 
from static DSLAM port config, and to @isp.com dynamic routing?

>
> Currently, our Radius server resides at the head end of our PPPoE
> network. I would like to remove the chance that if the Internet failed
> there, that no one on the separate networks would be able to authenticate.

So the other networks have separate internet connectivity?

>
> Has anyone had any experience with using a Radius server in the cloud to
> authenticate users?

Personally, I'd never do it. FreeRADIUS performs well on commodity 
hardware, so just build more RADIUS servers and put them in various 
locations e.g. one in each remote location. Presumably you have DHCP 
servers in those locations now - the same hardware would probably 
suffice, since the load should be approximately the same.

However, as Fajar says, if you want to "cloud" it there's nothing magic 
- RADIUS is just UDP/IP packets, so running it in the cloud should work 
fine.

Couple of things to watch out for:

  1. RADIUS shared-secrets are keyed off source IP and destination 
IP/port. We occasionally see people who've painted themselves into a 
corner with NAT, or NASes on dynamic, unknown-prior IPs. Think carefully 
about how you'll avoid this issue, particularly if your NASes are on 
private IPs.

This is not usually a problem over an internal network.

  2. Normal radius doesn't encrypt (but does sign) the entire packet. 
Only selected fields like "User-Password" (and EAP payloads that are 
encrypted by the EAP method). Decide if you care about this - the RADIUS 
packet will contain things like user names, MAC addresses and so on, and 
they'll be flowing over an untrusted network. It's probably not a worry, 
but in the EU at least, I'd be concerned about data protection.

In theory you can solve this with RADSEC. In practice, virtually no NAS 
supports RADSEC, so you are left with IPSec or some other VPN as an 
option, or just live with it.

Likewise, not usually a problem over an internal network.